Abstract:To improve the efficiency of optical coupling and the signal-to-noise ratio of long wavelength quantum well infrared detector（LW-QWIP）， we designed and fabricated a quantum well subwavelength micropillar arrays structure targeting at 8.7 μm central wavelength. Different from the reported metal or dielectric microcavity structures， each pillar contains 50 periods of quantum wells and barriers， this， combined with the filling factor lower than 0.18， is expected to considerably suppress the dark current while enhancing the efficiency of light absorption. Infrared spectrum measurement discloses that the micropillar arrays reflect only 8% in the wavelength range of 8~9 μm. Our study offers a practical scheme for sensitive infrared detection at high operation temperature.

Abstract:Smaller Voc of 1.0eV/0.75 eV InGaAsP/InGaAs double-junction solar cell（DJSC） than the Voc sum of individual subcells has been observed， and there is little information of the origin of such Voc loss and how to minimize it. In this paper， it is disclosed that the dominant mechanism of minority-carrier transport at back-surface-field（BSF）/base interface of the bottom subcell is thermionic emission， instead of defect-induced recombination， which is in contrast to previous reports. It also shows that both InP and InAlAs cannot prevent the zinc diffusion effectively. In addition， intermixing of major III-V element occurs as a result of increasing thermal treatment. To suppress the above negative effects， an initial novel InP/InAlAs superlattice（SL） BSF layer is then proposed and employed in bottom InGaAs subcell. The Voc of fabricated cells reach 997.5 mV， and a reduction of 30 mV in Voc loss without lost of Jsc， compared with the results of conventional InP BSF configuration， is achieved. It would benefit the overall Voc for further four-junction solar cells.

Abstract:The research on high power 110GHz single and power-combined frequency doublers based on discrete diodes is presented in this paper. The doubler with a single Schottky diode circuit has a measured peak efficiency of 33% and bandwidth over 13.6%. Meanwhile， two different architectures with two single devices adding in-phase have been utilized to realize the power-combined doublers. The combined doubler features four discrete Schottky diodes with twelve junctions altogether soldered on two 127μm-thick ALN substrates. Both devices have demonstrated output powers more than 200mW with a pumping power over 800mW and are capable of providing more power for higher driven power.

Abstract:In this study， we investigate the stress evolution and its effects on detection performance of self-rolled quantum well infrared detector. It is found that tensile stress can move the energy level of conduction band up， while compressive stress moves it down. The band movement of self-rolled film with double quantum wells depends on the change of resultant stresses in the two quantum wells. The rolled-up sample can effectively transform the stress change into strain， so as to weaken the impact of ambient temperature and enhance the stability of infrared devices. The wrinkled film has higher compressive stress compared with the rolled-up sample， which results in lower responsivity. When the same bias voltage is applied， the voltage responsivity of the rolled-up sample is about 2.5 times higher than that of the wrinkled sample.

Abstract:Concentrating on the high frequency demands of solid-state power amplifier （SSPA） for space usage， the methodology and key techniques of the Q band 20 watts， V band 10 watts and W band 2 watts SSPAs were proposed in the present study. The GaN HEMT monolithic microwave integrated circuits （MMICs） are utilized as basic power amplifier units for power and efficiency enhancement. The high efficiency multi-ways low loss power combination techniques including magic T and radial-line were developed to achieve high output power. Copper diamond and heat pipes were applied to overcome heat dissipation and thermal flux challenges. By considering the strictly space qualification and components derating requirements， all products show state-of-art performances， which are used and verified in application for satellites payloads or terminal transmitters. To the authors knowledge， this is the first time the EHF band SSPA are developed and qualified for space usage in China. The designs proposed in the paper meet the demands and requirements for future satellite projects， to strongly support high frequency and high throughput space communication tendency and targets realization.

Abstract:This paper presents a millimeter-wave microstrip-based sub-harmonic mixer with a wide operation band. In this design， frequency suppression circuits including a wideband bandpass short-circuited filter and a diplexer are employed not only to provide proper terminations for the intermediate frequency （IF）， radio frequency （RF）， and local oscillator （LO） signals simultaneously， but also to reject the major idle mixing products. The measured results show that the proposed sub-harmonic mixer can support the operations in RF band from 27 to 48 GHz， and in IF band up to 6 GHz. Meanwhile， the conversion loss is less than 12.5 dB for both up- and down- conversion throughout the bandwidth， in which， the minimum conversion loss is about 7.5 dB and 8.2 dB for the down-conversion and up-conversion， respectively， at an RF of 33 GHz and IF of 1 GHz.

Abstract:The spectral characteristics of aluminium oxide （Al2O3） in broadband terahertz wave range （0.2~3.0 THz） were investigated by using terahertz time-domain spectroscopy （THz-TDS）. The terahertz time-domain spectra of Al2O3 crystal at different azimuthal angles is obtained by changing the angle between the crystal optical axis and the polarization direction of THz pulse. The refractive index and absorption coefficient of o- and e-waves are calculated， and the index ellipse of Al2O3 in THz band is drawn. The experimental results indicate that Al2O3 has large birefringence and low absorption coefficient in THz， with a birefringence as high as 0.36 and an absorption coefficient lower than 5 cm-1. The phase and amplitude of THz pulse can be modulated based on the birefringence of the crystal. Al2O3 crystal can be used as "shaper" of THz pulse， which provides important reference for the application of terahertz wave in ultra-wideband and ultra-high speed communication systems.

Abstract:In order to obtain the widest wavelength tuning range， the cavity length of the tunable Fabry-Perot filter （TFPF） must be very small when used as a spectroscopic device in hyperspectral remote sensing. Differently from conventional Fabry–Perot interferometer， phase change occurring on reflection at each mirror can not be neglected when the cavity length is comparable with the resonant wavelength. In this paper， numerical calculations were carried out for the reflection phase shift on dielectric mirrors and filtering performance of TFPF in wide spectral range based on the Transfer-Matrix Method. Results show that TFPF exhibits higher spectral resolution and compressed wavelength tuning range after considering reflection phase shift. These research achievements can provide guidance for structure design and wavelength calibration of TFPF for hyperspectral remote sensing applications.

Abstract:High-quality semiconductor thin films are the basis for high-performance optoelectronic devices, of which the optoelectronic properties are restricted by the substrates. Experimental evaluation of the substrate beneath the thin films is therefore crucial for optimizing film growth. Unfortunately, such evaluation of substrates is usually severely affected by the capping thin films. This paper reports a Fourier transform (FT) Raman spectroscopic method, which utilizes the deep penetration characteristics of infrared pumping light with low photon energy, reduces the influence of the capping film, and extracts the Raman scattering information of the semiconductor substrate effectively. Application to CdTe thin films on GaAs-substrate demonstrates suppression of the CdTe while enhancement of the GaAs-substrate Raman scattering, as compared to a conventional Raman method. The signal-to-noise ratio of the spectrum exceeds 70, indicating the FT-Raman method a feasible approach for experimentally probing semiconductor substrate beneath thin films and/or multilayer structure.

Abstract:In this paper， a novel interpolation-based subpixel mapping （ISPM） for hyperspectral image by using pansharpening （PAN-ISPM） is proposed. In the proposed method， a novel processing path is added into the existing processing path of ISPM. Firstly， the original coarse hyperspectral image is improved by pansharpening technique in the novel processing path， and the novel fine fraction images are derived by unmixing the improved image. Secondly， the novel fine fraction images from the novel path and the existing fine fraction images from the existing path are integrated to produce the finer fraction images with more spatial-spectral information. Finally， according to the predicted values from the finer fraction images， class labels are allocated into subpixel to obtain the final mapping result. Experimental results show that the proposed method produces the higher mapping accuracy than the existing ISPM methods.

Abstract:In order to solve the problem that the optical center of hyperspectral images does not coincide with each other， and the alignment of traditional global monotonic matrix may have error in the registration process， a splicing-method （H-SPHP） of hyperspectral images based on SPHP（shape-preserving half-projective） and considering spectral information is proposed. The main steps include as follows： 1） image correction using the visual vector method. 2） selection of reference band based on prior knowledge and PCA. 3） SPHP-based mesh optimization splicing method. 4） Weighted average fusion algorithm for fusion.5） splicing parameters applied to all bands to obtain the splicing hyperspectral data. By obtaining experimental images from Sanming， Fujian province and Nanchang，Jiangxi province， the research data splicing experimental results show that the proposed algorithm has strong robustness， eliminating parallax and geographic coordinates accuracy better than SIFT + single should transform algorithm. After splicing， the registration accuracy of bands is within one pixel， and spectral similarity of the overlapping region is above 90%.

Abstract:In view of the low spatial resolution of passive microwave soil moisture （SM） data， statistical and physical models including random forest （RF）， polynomial fitting and DISPATCH are utilized to disaggregate the FY3B microwave SM product from 25 km to 1 km with the synergistic application of Optical/Thermal infrared （TIR） observations and surface elevation parameters. Meanwhile， considering different overpass times of FY3B and other relevant input data source observations， four data combinations are separately used to derive the spatially downscaled SM with above three downscaling method， and the optimized data combination of FY-3B downscaling is proposed by comparison and analysis. Validation is performed from April 1， 2015 to December 31， 2016 with the in-situ measurements of REMEDHUS network and the precipitation time series of ECA&D meteorological site. Experimental results show that RF-based method can achieve the highest comprehensive downscaling accuracy and the best model fitting effect. In addition， the effect of applying FY-3B ascending data to downscale turns out to be better.

Abstract:A triple imaging infrared continuous zoom array detector scanning optical system is proposed. On the basis of traditional infrared secondary imaging optics, a continuous zoom telescope system is added. Continuous zoom is realized by moving the zooming group and the compensating group along the optical axis. In the middle parallel light path, a galvanometer is introduced, and the galvanometer is used to scan back in the corresponding angle range at a specific frequency, which can compensate for the object movement during the exposure time caused by the rotation of the scanning platform, and keep the image clear and stable during the rotation scanning without any shadow. A 60~360 mm continuous zoom optic system is designed. Optic distortion is smaller than 0.5% at all effective focal length. The system achieved good performance after testing, and can be widely used in the infrared search and tracking system.

Abstract:Sea fog， as an important factor affecting the transmittance of the atmosphere， reduces the contrast between the ship targets and the sea-surface background in the infrared detection of ship targets on the sea. The traditional detection method based on infrared intensity cannot obtain ship targets as the contrast is less than the detection threshold with the increase of sea fog concentration. In view of the above situations， a background radiation suppression method based on sea surface polarimetric characteristics was developed to enhance the contrast according to the polarimetric characteristics of the sea fog scene. First， the relationship between the atmospheric transmittance of sea fog and infrared thermal radiation under different conditions is analyzed. Then， by analyzing the polarization characteristics of the sea surface radiation， a numerical model of the scene based on polarization contrast and intensity contrast was established. Finally， Analyzing the change regulation of threshold transmittance （） and contrast improvement （） under the circumstances of different detection angles， detection heights， and temperature differences between ship targets and sea surface. The simulation results indicate that gradually increases with the temperature difference and the detection angle decrease， along with the difference between the intensity and the polarization . but the intensity is always greater than the polarization . Therefore， the method provides a useful reference for ship detection in the sea fog environment with low atmospheric transmittance.

Abstract:Optical vortex is normally generated via a beam shaping process by irradiating a Gaussian beam through an external optical element or structure. Laser induced photorefractive structures can direct endow beam shaping functions inside materials， which can be stable and easy for the integration of devices. However， this is a method based on linear diffraction and normally cannot obtain efficient second harmonic optical vortex. To solve this problem， firstly， the effects of laser writing parameters on the resolution and maximal depth of photorefractive structures were experimentally investigated in lithium niobite. As a proof of concept， cross-shaped second harmonic vortex beams were obtained by illuminating a fundamental Gaussian beam through a 3D fork hologram. Then it was theoretically demonstrated that phase-matched second harmonic vortex beams can be generated by utilizing the Bragg diffraction of fundamental beam in the wavelength range between 1.074~3.716 μm.

Abstract:A novel Graphics Processing Units （GPU） accelerated level set model which organically combines the global fitting energy and the local fitting energy from different models and the weighting coefficient of the global fitting term can be adaptively adjusted， is proposed to image segmentation. The proposed model can efficiently segment images with intensity inhomogeneity regardless of where the initial contour lies in the image. In its numerical implementation， an efficient numerical scheme called Lattice Boltzmann Method （LBM） is used to break the restrictions on time step. In addition， the proposed LBM is implemented by using a NVIDIA GPU to fully utilize the characteristics of LBM method with high parallelism. The extensive and promising experimental results from synthetic and real images demonstrate the effectiveness and efficiency of the proposed method.In addition， the factors that can have a key impact on segmentation performance are also analyzed in depth.

Abstract:Point target detection in Infrared Search and Track (IRST) is a challenging task, due to less information. Traditional methods based on hand-crafted features are hard to finish detection intelligently. A novel deep spatial-temporal convolution neural network is proposed to suppress background and detect point targets. The proposed method is realized based on fully convolution network. So input of arbitrary size can be put into the network and correspondingly-sized output can be obtained. In order to meet the requirement of real time for practical application, the factorized technique is adopted. 3D convolution is decomposed into 2D convolution and 1D convolution, and it leads to signi?cantly less computation. Multi-weighted loss function is designed according to the relation between prediction error and detection performance for point target. Number-balance weight and intensity-balance weight are introduced to deal with the imbalanced sample distribution and imbalanced error distribution. The experimental results show that the proposed method can effectively suppress background clutters, and detect point targets with less runtime.

Abstract:Multi-view stereo reconstruction relies on object’ s surface feature， and thus occurred data deficiency in dealing with low-texture regions， the polarization characteristics of the reflection light be fused to observe completely surface under different light surroundings， which can reconstruct depth map of objects by calculating polarization parameters and normal information. However， there appears several problems such as azimuth ambiguity and zenith angle deviation using pure polarization information for 3D reconstruction， which result in distortion of the reconstruction results and even couldn’t get the depth. For objects with low-texture regions， capturing images from around 30 views from four polarizing angles using polarization camera， and using parallax bundle adjustment to optimize camera parameters and points’ coordinate and using passion optimization method to correct zenith angle deviation， the 3D reconstruction algorithm combining the multi-view stereo and polarization information can not only replenish the local data deficiency of multi-view 3D point cloud， but also solve the azimuth ambiguity and zenith angle deviation， and finally get the more accurate 3D reconstruction results.